Metabolic syndrome or MetS is largely responsible for the epidemic of cardiovascular disease and diabetes that’s exploding throughout the developed and developing worlds.
This insidious syndrome is defined by the presence of three or more of a half-dozen metabolic risk factors:
Abdominal obesity (excessive fat in and around the abdomen).
High blood triglycerides, low HDL cholesterol and high LDL cholesterol.
Elevated blood pressure.
Insulin resistance or glucose intolerance.
Pro-thrombotic state that promotes dangerous clots.
Pro-inflammatory state in the blood.
We’ve reported on how certain foods and nutrients might affect development of MetS … see the “Omega-3s & Metabolic Health,” “Vitamin D & Metabolic Health,” and “Foods & Metabolic Health” sections of our news archive.
Milk and dairy products appear to be allies in the fight against this dangerous cluster of risk factors.
We hasten to add that fermented milk products like yogurt, kefir, and buttermilk should be favored over regular milk products.
This is because fermented milk products are easier to digest and offer “probiotic” cultures that benefit digestive and overall health.
Now, the results of a clinical trial suggest that dairy foods may play a positive role as allies against diabetes ... see “Clinical trial details key anti-diabetes effects of dairy”, below.
Following that review of the new research, we'll address some of the oft-repeated attacks on milk and milk products, with an anti-dairy Huffington Post article by Mark Hyman, M.D., as our foil.
Dairy foods may reduce pre-diabetes “metabolic syndrome”
A growing body of evidence suggests that people whose diets contain relatively high proportions of milk products are less likely to develop insulin resistance… or diabetes, for which insulin resistance is the leading risk factor.
The same is true of people who have relatively high body levels of calcium and vitamin D – which often come from high milk-product intake.
(Fatty wild fish like salmon, tuna, and sardines – but not farmed fish – has far more vitamin D than milk does, but excepting tuna, Americans don’t eat very much fatty wild fish.)
A recent evidence review found that people reporting the highest dairy intakes – 3 to 4 servings per day – were 29 percent less likely to develop insulin resistance, vs. those reporting only 0.9-1.7 servings per day (Tremblay A, Gilbert JA 2009).
Overall, as the review authors concluded, “...the intake of low-fat dairy products… has been shown to contribute to a significant extent to the prevention of insulin resistance syndrome” (Tremblay A, Gilbert JA 2009).
And findings reported last year from Harvard showed that people with the highest blood levels of trans-palmitoleic acid – a monounsaturated fatty acid found primarily in milk products – were the least likely to have adult-onset (type II) diabetes.
(For more on that research, see “Does Milk Help Deter Diabetes?”)
Clinical trial details key anti-diabetes effects of dairy
The findings of experimental studies from Japan and the University of Tennessee found reduced oxidative stress and inflammation – two key components of the pre-diabetic condition called metabolic syndrome – in rodents fed dairy foods (Furukawa S et al. 2004; Zemel MB et al. 2008)
As the Japanese team wrote, “increased oxidative stress in accumulated fat is an early instigator of metabolic syndrome” (Furukawa S et al. 2004)
But animal studies don’t always translate to humans, so the positive outcomes of a new clinical trial from the University of Tennessee seem significant.
The results of this trial show that eating “adequate” amounts of dairy foods (3.5 daily servings) reduced oxidative stress and inflammation in overweight people who already showed signs of metabolic syndrome (Stancliffe RA et al. 2011).
The authors of the trial set out to determine the short-term (seven-day) and sustained (four week and 12 week) effects of an “adequate-dairy” diet compared with a “low-dairy” diet in people with metabolic syndrome.
The Tennessee team recruited 40 overweight and obese adults with metabolic syndrome, who were randomly assigned to one of two moderate-calorie, “weight-maintenance” diets:
Adequate-Dairy (AD) – 3.5 daily servings of dairy.
Low-Dairy (LD) – less than 1/2 daily serving of dairy.
The scientists measure blood markers for oxidative stress (MDA and oxidized LDL cholesterol) and inflammation (TNF-alpha, IL-6, and MCP-1) at the outset and again after one, four, and 12 weeks.
They also measured body weight and composition at the same intervals.
The AD group showed lower blood levels of oxidation markers (MDA and oxidized LDL) after 7 days – 35 percent and 11 percent lower, respectively – with further decreases after 12 weeks.
Inflammation markers were also lowered in the AD group, with decreases in TNF-alpha at 7 days and further reductions through 12 weeks (35 percent); decreases in IL-6 (21 percent) and MCP-1 (24 percent decrease after 12 weeks).
The Adequate-Dairy group also showed decreases in waist circumference and abdominal fat.
Importantly, the Adequate-Dairy group also enjoyed a 55 percent increase in levels of adiponectin – a hormone proven to help prevent insulin resistance and diabetes – after 12 weeks.
In contrast, the Low-Dairy group showed no reductions in the markers for oxidative stress or inflammation, and no effect on adiponectin levels, body weight, waist circumference, or abdominal fat.
As the authors, wrote, “An increase in dairy intake attenuates oxidative and inflammatory stress in metabolic syndrome.” (Stancliffe RA et al. 2011)
White this study was funded by the U.S. National Dairy Council, its results fit with prior findings not supported by commercial interests.
Let’s look at some of the common but generally unfounded myths about milk held by many in the natural health community.
The demonization of dairy
Since the early 1970’s, milk, butter, and other dairy foods have been accused of promoting heart disease because they are high in saturated fats.
But the saturated fat theory of heart disease is increasingly discredited ... see “Saturated Fat Seen as Heart Red Herring” and “Cholesterol Fiasco Undermines Accepted Theory.”
And some in the natural health community – who may not accept the saturated fat theory of heart disease – still demonize milk products, though for different reasons.
Their case against milk is summarized in a May 2010, Huffington Post article by Mark Hyman, M.D., who cites six reasons to avoid cow’s milk … even cultured milk products like yogurt and kefir (Hyman M 2010).
Dr. Hyman has been a good advocate for smart eating … but his critique encapsulates the misguided fear of milk and dairy foods found among many in the natural health world.
The case against milk … it’s weak, at best
Most of Dr. Hyman’s critique simply notes that milk is not as marvelous as claimed in the Dairy Council’s “Got Milk?” campaign or as implied in the old USDA food pyramid.
(It’s no surprise that these two bodies – which share the goal of boosting milk sales – tend to exaggerate its benefits.)
And we agree with Dr. Hyman that milk is not nearly as helpful to bone health as pro-milk propaganda would have consumers believe.
However, Dr. Hyman repeats a common accusation that dairy causes the body to generate excess mucous and promotes allergies or asthma.
Weirdly, the evidence review from New Zealand that he cites as evidence for this assertion doesn’t actually support it:
“Excessive milk consumption has a long association with increased respiratory tract mucus production and asthma. Such an association cannot be explained using a conventional allergic paradigm and there is limited medical evidence showing causality.” (Bartley J, McGlashan SR 2009).
And Dr. Hymn overlooked an evidence review by Austrian scientists, who found no evidence that milk products generate excess mucous or promote allergies and asthma:
“In individuals inoculated with the common cold virus, milk intake was not associated with increased nasal secretions, symptoms of cough, nose symptoms or congestion … the consumption of milk does not seem to exacerbate the symptoms of asthma and a relationship between milk consumption and the occurrence of asthma cannot be established.” (Wüthrich B et al. 2005)
Of course, as the Austrians noted, belief is a powerful thing: “Nevertheless, individuals who believe in the mucus and milk theory report more respiratory symptoms after drinking milk.” (Wüthrich B et al. 2005)
And it goes without saying that few rules about food and health are completely universal, because a person’s unique combination of genes, physiology, health status, and diet can produce uncommon outcomes.
Accordingly, the New Zealand team acknowledged that an unlikely but possible set of prerequisites could explain why, as they wrote “… a subgroup of the population, who have increased respiratory tract mucus production, find that many of their symptoms, including asthma, improve on a dairy elimination diet.” (Bartley J, McGlashan SR 2009)
Milk promotes cancer? Not likely
In his attack on milk, Dr. Hyman made this very odd assertion as one of his six reasons to avoid dairy: “Calcium may raise cancer risk” (Hyman M 2010).
To support this accusation, he cites evidence that “higher intakes of both calcium and dairy products may increase a man's risk of prostate cancer by 30 to 50 percent. Plus, dairy consumption increases the body’s level of insulin-like growth factor-1 (IGF-1) … a known cancer promoter.”
To be sure, the authors of the epidemiological study he cites did link higher dairy consumption to greater rates of advanced prostate cancer … but that association was limited to low-fat milk, not whole milk (Tseng M et al. 2005).
But milk isn't likely the reason for that correlation. Harvard researchers who analyzed data from 47,750 male physicians detected a statistical association between higher calcium intake and greater risk of rare, advanced prostate cancer, they linked that risk to a lowering of vitamin D levels caused by high calcium intake (more than 1500mg daily), rather than to milk. (Giovannucci E et al. 2006)
In an earlier analysis, some of the same Harvard scientists concluded, “Dairy intake was not associated with prostate cancer risk.” (Rodriguez C et al. 2003)
And another Harvard team who looked at breast cancer and dairy found “…no association between intake of dairy products and breast cancer in postmenopausal women. Among premenopausal women, high intake of low-fat dairy foods, especially skim/low-fat milk, was associated with reduced risk of breast cancer.” (Shin MH et al. 2002)
Conversely, milk is associated with reduced risk of colon cancer, which is generally far more dangerous than prostate cancer … so a broad assertion that “calcium may raise cancer risk” is grossly inaccurate, to say the least (Kampman E et al. 2000; Park SY et al. 2007).
As to the assertion about IGF-1 – which is a normal human hormone, not a carcinogen per se – a clinical study published earlier this year found no rise in IGF-1 levels among women who consumed yogurt before and after exercise daily for 16 weeks (Thomas DT et al. 2011).
However, in another clinical study, soy foods including soy milk, did raise IGF-1 levels among premenopausal women (Maskarinec G et al. 2009).
Bartley J, McGlashan SR. Does milk increase mucus production? Med Hypotheses. 2010 Apr;74(4):732-4. Epub 2009 Nov 25.
Furukawa S, Fujita T, Shimabukuro M, Iwaki M, Yamada Y, Nakajima Y, Nakayama O, Makishima M, Matsuda M, Shimomura I. Increased oxidative stress in obesity and its impact on metabolic syndrome. J Clin Invest. 2004 Dec;114(12):1752-61.
Giovannucci E, Liu Y, Stampfer MJ, Willett WC. A prospective study of calcium intake and incident and fatal prostate cancer. Cancer Epidemiol Biomarkers Prev. 2006 Feb;15(2):203-10.
Hyman M. Dairy: 6 Reasons You Should Avoid It at All Costs or Why Following the USDA Food Pyramid Guidelines is Bad for Your Health. May 1, 2010. Accessed at http://www.huffingtonpost.com/dr-mark-hyman/dairy-free-dairy-6-reason_b_558876.html
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Rodriguez C, McCullough ML, Mondul AM, Jacobs EJ, Fakhrabadi-Shokoohi D, Giovannucci EL, Thun MJ, Calle EE. Calcium, dairy products, and risk of prostate cancer in a prospective cohort of United States men. Cancer Epidemiol Biomarkers Prev. 2003 Jul;12(7):597-603.
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Thomas DT, Wideman L, Lovelady CA. Effects of a dairy supplement and resistance training on lean mass and insulin-like growth factor in women. Int J Sport Nutr Exerc Metab. 2011 Jun;21(3):181-8.
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Zemel MB, Sun X. Dietary calcium and dairy products modulate oxidative and inflammatory stress in mice and humans. J Nutr. 2008 Jun;138(6):1047-52.